Electromagnetic wave measuring apparatus and electromagnetic wave measuring method

Abstract

To satisfactorily measure an electromagnetic wave while changing the frequency of light beams from a light source.SOLUTION: An electromagnetic wave measuring apparatus includes: a light source section that outputs a first laser beam whose frequency is settable, and a second laser beam; an electro-optic probe that receives the first laser beam of frequency that is set in a frequency range, the second laser beam, and an electromagnetic wave to be detected; an optical filter; and a light-receiving element that converts light that has passed through the optical filter into an electrical signal. The electro-optic probe outputs the first laser beam, the second laser beam, a first sideband beam, and a second sideband beam. The optical filter attenuates a frequency component of at least one of the first laser beam and the second sideband beam, or a frequency component of at least one of the second laser beam and the first sideband beam.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electromagnetic wave measuring device and an electromagnetic wave measuring method. [Background technology]

[0002] Various devices for detecting electromagnetic waves using electro-optic crystals and the like have been developed. As an example of such a technology for detecting electromagnetic waves, for example, Patent Document 1 (JP Patent Publication No. 2017-015703) discloses the following technology. That is, an electromagnetic wave measuring device includes a light source, an electro-optic probe that receives light from the light source and electromagnetic waves, an optical filter that receives light output from the electro-optic probe, and a light receiving element that converts light that has passed through the optical filter into an electrical signal, and the electro-optic probe includes an electro-optic crystal and an optical fiber optically coupled to the electro-optic crystal, and is provided so that the direction of the inherent axis of the electro-optic crystal and the polarization direction of the light from the optical fiber that is incident on the electro-optic crystal are aligned. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-015703 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need for a technique that goes beyond the technique described in Patent Document 1 and is capable of measuring electromagnetic waves while flexibly responding to changes in the frequency of light from a light source.

[0005] The present invention has been made to solve the above-mentioned problems, and its object is to provide an electromagnetic wave measuring device and an electromagnetic wave measuring method that are capable of measuring electromagnetic waves while flexibly responding to changes in the frequency of light from a light source. [Means for solving the problem]

[0006] (1) In order to solve the above problem, an electromagnetic wave measurement device according to an aspect of the present invention includes a light source unit that outputs first laser light and second laser light, the frequencies of which can be set within a predetermined frequency range; an electro-optical probe that receives the first laser light, the second laser light, and a detectable electromagnetic wave, each having a frequency set within the frequency range; an optical filter that receives the light output from the electro-optical probe and attenuates frequency components outside a predetermined passband; and a light-receiving element that converts the light that has passed through the optical filter into an electric signal, wherein the electro-optical probe outputs the first laser light, the second laser light, a first sideband light generated by modulating the first laser light, and a second sideband light generated by modulating the second laser light to the optical filter, and the optical filter attenuates at least one of the frequency components of the first laser light and the second sideband light, or attenuates at least one of the frequency components of the second laser light and the first sideband light, as the frequency components outside the passband.

[0007] In this manner, the first laser light, the second laser light, and the electromagnetic wave to be detected, the frequencies of which can be set within a predetermined frequency range, are provided to the electro-optical probe, and a filtering process is performed to attenuate at least one of the frequency components of the first laser light and the second sideband light, or at least one of the frequency components of the second laser light and the first sideband light, which are set within the frequency range, among the light output from the electro-optical probe. Even if the frequency of the first laser light is changed within the frequency range, the filtering process can be performed using the same optical filter to obtain a beat signal containing information such as the electric field of the electromagnetic wave to be detected. Therefore, the electromagnetic wave can be measured while flexibly responding to changes in the frequency of the light from the light source.

[0008] (2) In the above (1), the optical filter may be a bandpass filter, and the optical filter may attenuate at least one of the frequency components of the first laser light and the second sideband light as frequency components outside the passband.

[0009] With this configuration, even if the frequency of the first laser light is changed, the second laser light and the first sideband light can be extracted using the same optical filter without changing the optical filter. Furthermore, since the passband of the optical filter can be narrowed compared to a configuration using a band elimination filter as the optical filter, it is possible to satisfactorily measure the electromagnetic wave using the first laser light set to a suitable frequency while suppressing a decrease in the SNR (Signal-to-Noise Ratio) of the beat signal caused by setting the passband of the optical filter to a wide range.

[0010] (3) In the above (1), the optical filter may be a band elimination filter, and the optical filter may attenuate at least one of a frequency component of the second laser light and a frequency component of the first sideband light as a frequency component outside the passband.

[0011] With this configuration, even if the frequency of the first laser light is changed, the first laser light and the second sideband light can be extracted using the same optical filter without changing the optical filter.

[0012] (4) In any one of (1) to (3) above, the passband of the optical filter may be configured not to overlap with the frequency range.

[0013] With this configuration, it is possible to use the optical filter to extract a desired frequency component from the frequency components of the light output from the electro-optic probe while appropriately selecting the frequency of the first laser light within the frequency range.

[0014] (5) In any of (1) to (4) above, the electromagnetic wave measuring device may further include an optical shifter that shifts the frequency of the first laser light, and an optical-electromagnetic wave conversion unit that irradiates the electro-optical probe with an electromagnetic wave having a frequency that is the difference between the frequency of the first laser light whose frequency has been shifted by the optical shifter and the frequency of the second laser light.

[0015] With this configuration, the self-heterodyne electromagnetic wave measuring device can measure electromagnetic waves while flexibly responding to changes in the frequency of light from the light source. Also, compared to a configuration in which the frequency of the second laser light is shifted instead of the frequency of the first laser light, the SNR of the obtained beat signal can be improved, so that electromagnetic waves in the terahertz region can be measured with higher accuracy.

[0016] (6) In any of (1) to (4) above, the electromagnetic wave measuring device may further include an optical shifter that shifts the frequency of the second laser light, and an optical-electromagnetic wave conversion unit that irradiates the electro-optical probe with an electromagnetic wave having a frequency that is the difference between the frequency of the first laser light and the frequency of the second laser light whose frequency has been shifted by the optical shifter.

[0017] With this configuration, in a self-heterodyne type electromagnetic wave measuring device, it is possible to measure electromagnetic waves while flexibly responding to changes in the frequency of light from the light source.

[0018] (7) In any one of (1) to (6) above, the light source unit may output the second laser light having a settable frequency.

[0019] With this configuration, more diverse electromagnetic wave measurements can be performed using two types of laser light with adjustable frequencies.

[0020] (8) In order to solve the above-mentioned problems, an electromagnetic wave measuring method according to an aspect of the present invention is an electromagnetic wave measuring method in an electromagnetic wave measuring device, the method including the steps of: setting a frequency in a predetermined frequency range; generating first laser light and second laser light having the frequency set in the frequency range; providing the generated first laser light and second laser light, as well as a detected electromagnetic wave, to an electro-optic probe; attenuating frequency components outside a predetermined passband of light output from the electro-optic probe using an optical filter; and converting the light that has passed through the optical filter into an electric signal using a light receiving element. the electro-optical probe outputs the first laser light, the second laser light, a first sideband light generated by modulating the first laser light, and a second sideband light generated by modulating the second laser light to the optical filter, and in the step of attenuating frequency components outside the passband, at least one of a frequency component of the first laser light and a frequency component of the second sideband light is attenuated as the frequency components outside the passband, or at least one of a frequency component of the second laser light and a frequency component of the first sideband light is attenuated.

[0021] In this way, by providing the electro-optic probe with the first laser light, the second laser light, and the detectable electromagnetic wave, the frequencies of which can be set within a predetermined frequency range, and performing a filtering process to attenuate at least one of the frequency components of the first laser light and the second sideband light, or at least one of the frequency components of the second laser light and the first sideband light, which are set within the frequency range, among the light output from the electro-optic probe, even if the frequency of the first laser light is changed within the frequency range, the filtering process can be performed using the same optical filter to obtain a beat signal containing information such as the electric field of the detectable electromagnetic wave. Therefore, it is possible to measure the electromagnetic wave while flexibly responding to changes in the frequency of the light from the light source. Effect of the Invention

[0022] According to the present invention, it is possible to measure electromagnetic waves while flexibly responding to changes in the frequency of light from a light source. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a configuration of an electromagnetic wave measuring device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing an example of a passband of an optical filter in the electromagnetic wave measuring device according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a configuration of an electromagnetic wave measuring device according to a first modification of the first embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the first modification of the first embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of a passband of an optical filter in the electromagnetic wave measuring device according to the first modification of the first embodiment of the present invention. In FIG. [Figure 7] FIG. 7 is a diagram showing a configuration of an electromagnetic wave measuring device according to a second modification of the first embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the second modification of the first embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to a second modification of the first embodiment of the present invention. In FIG. [Figure 10] FIG. 10 is a diagram showing a configuration of an electromagnetic wave measuring device according to a third modification of the first embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the third modification of the first embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to a third modification of the first embodiment of the present invention. In FIG. [Figure 13] FIG. 13 is a diagram showing a procedure of an electromagnetic wave measuring method using the electromagnetic wave measuring device according to the first embodiment of the present invention. [Figure 14] FIG. 14 is a diagram showing a configuration of an electromagnetic wave measuring device according to the second embodiment of the present invention. [Figure 15] FIG. 15 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters and their description will not be repeated. In addition, at least some of the embodiments described below may be arbitrarily combined.

[0025] <First embodiment> [Configuration and basic operation] FIG. 1 is a diagram showing a configuration of an electromagnetic wave measuring device according to a first embodiment of the present invention. Referring to FIG. 1, the electromagnetic wave measuring device 201 includes optical amplifiers 3 and 4, optical splitters 5 and 6, optical multiplexers 7 and 8, an optical shifter 9, an oscillator 11, a circulator 12, a light receiving element 14, an amplitude / phase detector 15, an optical-electromagnetic wave converting unit 20, an electro-optical probe 51, a light source unit 101, and an optical filter 111. The light source unit 101 includes light emitting elements 1a and 2a, and a control unit 31. The optical-electromagnetic wave converting unit 20 includes an opto-electrical converter 21 and an antenna 22. The antenna 22 is, for example, a horn antenna. The electromagnetic wave measuring device 201 is a self-heterodyne type electromagnetic wave measuring device. The thick line in FIG. 1 indicates an optical fiber 16. This also applies to the subsequent drawings.

[0026] Optical transmission between the components of the electromagnetic wave measuring device 201 may be performed using optical fibers 16 or may be performed by spatial transmission. An example of spatial transmission is a configuration in which an electro-optic crystal member is disposed on a semiconductor integrated circuit that outputs the electromagnetic wave 36 to be detected, and the member is irradiated with probe light focused by an objective lens.

[0027] The light source unit 101 outputs laser light R1, the frequency of which can be set, and laser light R2. The laser light R1 outputted by the light source unit 101 is an example of a first laser light. The laser light R2 outputted by the light source unit 101 is an example of a second laser light.

[0028] More specifically, the light-emitting element 1a outputs a laser beam R1 having a frequency f1. The light-emitting element 2a outputs a laser beam R2 having a frequency f2. The light-emitting element 1a is, for example, a wavelength-variable laser, and the frequency f1 of the laser beam R1 can be set within a predetermined frequency range Rf1. More specifically, a user of the electromagnetic wave measuring device 201 determines the frequency f1 of the laser beam R1 to be used, for example, according to an object to be measured by the electromagnetic wave measuring device 201. The control unit 31 receives the setting contents of the fixedly set frequency f1 from the user, and controls the frequency f1 of the laser beam R1 output by the light-emitting element 1a according to the received setting contents. The light-emitting element 2a is, for example, a wavelength-fixed laser, and the frequency f2 of the laser beam R2 is set to a predetermined value.

[0029] For example, the frequency range Rf1 is determined by the specifications of the photoelectric converter 21. More specifically, the lower limit of the frequency range Rf1 is (f2-PinMAX) Hz, and the upper limit of the frequency range Rf1 is (f2-Pinmin) Hz. Here, Pinmin is the lower limit of the frequency difference between the laser beams R1 and R2 that can be input to the photoelectric converter 21, and PinMAX is the upper limit of the frequency difference between the laser beams R1 and R2 that can be input to the photoelectric converter 21.

[0030] The frequency f1 and the frequency f2 are, for example, frequencies in the 1.5 μm band. The difference between the frequency f1 and the frequency f2 is, for example, a frequency in the terahertz band. The difference between the frequency f1 and the frequency f2 may be a frequency other than the terahertz band, for example, a frequency in the microwave band or the millimeter wave band. In the following, the case where f2>f1 will be described as an example.

[0031] The optical amplifier 3 is, for example, an Erbium Doped Fiber Amplifier (EDFA), which amplifies the laser light R 1 outputted from the light source unit 101 and outputs the amplified laser light R 1 to the optical splitter 5 .

[0032] The optical splitter 5 splits the laser light R 1 received from the optical amplifier 3 , and outputs the split light to an optical shifter 9 and an optical multiplexer 8 .

[0033] The optical amplifier 4 is, for example, an EDFA, which amplifies the laser light R2 outputted from the light source unit 101 and outputs the amplified laser light R2 to the optical splitter 6.

[0034] The optical splitter 6 splits the laser light R2 received from the optical amplifier 4 and outputs the split light to the optical multiplexers 7 and 8.

[0035] The optical multiplexer 8 multiplexes the laser light R 1 received from the optical splitter 5 and the laser light R 2 received from the optical splitter 6 , and outputs the multiplexed light to the electro-optic probe 51 via the circulator 12 .

[0036] The oscillator 11 generates an oscillation signal with a frequency fs and outputs it to the optical shifter 9 and the amplitude / phase detector 15. The frequency fs is, for example, 500 kHz.

[0037] The optical shifter 9 shifts the frequency of the laser light R1. More specifically, the optical shifter 9 is provided on an optical transmission path between the light-emitting element 1a and the optical-electromagnetic wave conversion unit 20, and shifts the frequency of the received laser light R1 and outputs it. More specifically, the optical shifter 9 shifts the frequency of the laser light R1 received from the optical brancher 5 by the frequency fs of the oscillation signal received from the oscillator 11, and outputs the shifted laser light R1 to the optical multiplexer 7.

[0038] The optical multiplexer 7 multiplexes the laser light R 1 received from the optical shifter 9 and the laser light R 2 received from the optical splitter 6 , and outputs the multiplexed light to the optical-electromagnetic wave conversion unit 20 .

[0039] The optical / electromagnetic wave conversion unit 20 irradiates the electro-optical probe 51 with a detectable electromagnetic wave 36 having a frequency that is the difference between the frequency of the laser light R1, the frequency of which has been shifted by the optical shifter 9, and the frequency of the laser light R2. That is, the optical / electromagnetic wave conversion unit 20 receives the laser lights R1 and R2 from the optical multiplexer 7, generates a detectable electromagnetic wave 36 having a frequency that is the difference between the frequencies of the received laser lights R1 and R2, and irradiates the electro-optical probe 51 with the generated electromagnetic wave 36.

[0040] More specifically, the photoelectric converter 21 includes, for example, a photodetector, and generates a detectable electromagnetic wave 36 having a frequency component which is the difference between the frequencies of the laser beams R1 and R2 from the laser beams R1 and R2 received from the optical multiplexer 7, and irradiates the generated detectable electromagnetic wave 36 from the antenna 22 to the object to be measured.

[0041] The electro-optical probe 51 receives the laser beams R1, R2 and the electromagnetic wave 36 to be detected outputted by the light source unit 101. More specifically, the electro-optical probe 51 is disposed at a position where it can receive the electromagnetic wave irradiated from the antenna 22, such as a position facing the antenna 22. That is, the measurement target may be disposed between the antenna 22 and the electro-optical probe 51, may include the antenna 22, or may be the antenna 22 itself.

[0042] The electro-optical probe 51 detects the electromagnetic wave 36 to be detected. More specifically, the light transmitted from the circulator 12 to the electro-optical probe 51 interacts with the electromagnetic wave 36 to be detected from the antenna 22 in the electro-optical probe 51, and is reflected and output to the circulator 12, and then output from the circulator 12 to the optical filter 111.

[0043] The optical filter 111 receives the light output from the electro-optic probe 51 and attenuates frequency components outside a predetermined pass band F1. More specifically, the optical filter 111 attenuates components outside the pass band F1 among the frequency components of the light received from the circulator 12. For example, the optical filter 111 is a band pass filter.

[0044] The light receiving element 14 converts the light that has passed through the optical filter 111 into a beat signal Bs, which is an electrical signal, and outputs it to the amplitude / phase detector 15 .

[0045] The amplitude / phase detector 15 detects the amplitude and phase of the beat signal Bs received from the light receiving element 14 using the oscillation signal received from the oscillator 11, and outputs signals indicating the detected amplitude and phase. The amplitude / phase detector 15 can also detect the frequency of the beat signal Bs using the frequency of the probe light, for example, and output a signal indicating the detected frequency. The amplitude / phase detector 15 may be configured to detect one or two of the amplitude, phase, and frequency of the beat signal Bs received from the light receiving element 14.

[0046] In this way, the electromagnetic wave measuring device 201 can measure the spatial distribution of the electric field of the electromagnetic wave in a wide band from low to high frequencies by using optical technology, for example, by performing electromagnetic wave measurement while changing the position of the electro-optical probe 51. Also, the amplitude and phase of the electric field can be measured in real time.

[0047] In addition, the optical shifter 9 is not limited to being provided between the optical branching device 5 and the optical multiplexer 7, but may also be provided between the optical branching device 6 and the optical multiplexer 8, between the optical branching device 5 and the optical multiplexer 8, or between the optical branching device 6 and the optical multiplexer 7.

[0048] That is, the optical shifter 9 is provided between the light-emitting element 1a or the light-emitting element 2a and the optical-electromagnetic wave conversion unit 20 or the electro-optical probe 51, and shifts the frequency of the received light and outputs it. In other words, the optical shifter 9 shifts the frequency of the light from the light-emitting element 1a or the light-emitting element 2a and outputs it to the electro-optical probe 51 or the optical-electromagnetic wave conversion unit 20.

[0049] Furthermore, the electromagnetic wave measuring device 201 is not limited to a configuration including one optical shifter, and may be configured to include, for example, two optical shifters. Specifically, for example, in addition to the optical shifter 9, another optical shifter may be provided between the optical branching device 6 and the optical multiplexer 8, and the frequency shift directions of these optical shifters may be set in opposite directions. Furthermore, when the electromagnetic wave measuring device 201 includes two or more optical shifters, the frequency of the oscillation signal provided to the amplitude / phase detector 15 may be appropriately set according to the positions and shift directions of the optical shifters.

[0050] Fig. 2 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the first embodiment of the present invention. With reference to Fig. 1 and Fig. 2, electromagnetic wave measuring device 201 uses, for example, a CW (continuous wave).

[0051] More specifically, on the RF (Radio Frequency) side, i.e., in the system of the electromagnetic wave 36 to be detected, laser light R1 of frequency (f1+fs) is generated by the optical shifter 9, and the photoelectric converter 21 receives the laser light R1 of frequency (f1+fs) and the laser light R2 of frequency f2 that have been multiplexed in the optical multiplexer 7 (phase P1).

[0052] The photoelectric converter 21 performs photoelectric conversion (O / E), more specifically, generates a detectable electromagnetic wave 36 having a frequency component that is the difference between the frequencies of the two types of light received, i.e., a frequency of fT=f2-f1-fs (phase P2). The detectable electromagnetic wave 36 is irradiated in the direction of the electro-optic crystal in the electro-optic probe 51 (phase P12).

[0053] On the other hand, on the LO (Local) side, i.e., on the probe light system, the laser light R1 with frequency f1 and the laser light R2 with frequency f2 combined in the optical combiner 8 are transmitted as probe light to the electro-optic crystal in the electro-optic probe 51 (phases P11, P12).

[0054] The electro-optical probe 51 outputs the laser beams R1 and R2, the sideband beams R1s and R1sd generated by modulating the laser beam R1, and the sideband beams R2s and R2sd generated by modulating the laser beam R2 to the optical filter 111. The frequency of the sideband beam R1s is higher than the frequency of the sideband beam R1sd. The sideband beam R1s is a sideband beam having a frequency closest to the frequency f2 of the laser beam R2 among the sideband beams generated by modulating the laser beam R1. The frequency of the sideband beam R2s is lower than the frequency of the sideband beam R2sd. The sideband beam R2s is a sideband beam having a frequency closest to the frequency f1 of the laser beam R1 among the sideband beams generated by modulating the laser beam R2. The sideband beam R1s is an example of a first sideband beam, and the sideband beam R2s is an example of a second sideband beam.

[0055] More specifically, the frequency f1 component of the probe light is modulated in the electro-optic crystal irradiated with the electromagnetic wave 36 to generate sideband light R1s with a frequency component of f1s (=f1+fT=f2-fs) and sideband light R1sd with a frequency component of f1sd (=f1-fT). The frequency f2 component of the probe light is modulated in the electro-optic crystal irradiated with the electromagnetic wave 36 to generate sideband light R2s with a frequency component of f2s (=f2-fT=f1+fs) and sideband light R2sd with a frequency component of f2sd (=f2+fT) (phase P13). These generated lights are transmitted to the optical filter 111 together with the light with frequency f1 and the probe light with frequency f2 (phase P14).

[0056] The optical filter 111 attenuates the frequency components of the laser light R1 and the sideband light R2s as frequency components outside the passband F1. Specifically, the optical filter 111 attenuates frequency components other than the frequency components of the laser light R2 and the sideband light R1s as frequency components outside the passband F1. That is, the optical filter 111 extracts the laser light R2 with frequency f2 and the sideband light R1s with frequency f1s (phase P15).

[0057] FIG. 3 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to a first embodiment of the present invention. In FIG. 3, the horizontal axis is optical frequency [Hz]. Referring to FIG. 3, the optical filter 111 passes the laser light R2 of frequency f2 and the sideband light R1s of frequency f1s without attenuation, while attenuating the laser light R1 of frequency f1, the sideband light R2s of frequency f2s, the sideband light R1sd of frequency f1sd, and the sideband light R2sd of frequency f2sd. In this specification, "without attenuation" means that there is no attenuation for the purpose of filtering, and does not mean excluding normal transmission loss. For example, the passband F1 of the optical filter 111 does not overlap with the frequency range Rf1 in which the frequency f1 of the laser light R1 can be set.

[0058] 1 and 2, the light extracted by the optical filter 111 is transmitted to the photodetector 14 and undergoes photoelectric conversion (O / E), resulting in a beat signal Bs in the IF (Intermediate frequency) band of f2-f1s=fs (phase P21).

[0059] The optical filter 111 only needs to attenuate at least one of the laser light R1 with frequency f1 and the sideband light R2s with frequency f2s. As an example, the optical filter 111 may pass the sideband light R2s with frequency f2s without attenuating it, or may pass the sideband light R2sd with frequency f2sd without attenuating it. Even in this case, the beat signal Bs can be obtained in the light receiving element 14.

[0060] Referring to FIG. 1, amplitude / phase detector 15 is, for example, a lock-in amplifier having a mixer, a filter, a phase shifter, etc., and uses the oscillation signal of frequency fs received from oscillator 11 to generate a baseband electrical signal from IF band beat signal Bs received from photodetector 14, and detects the amplitude and phase of IF band beat signal Bs.

[0061] In this manner, the electromagnetic wave measuring device 201 makes it possible to measure the electric field of the electromagnetic wave 36 to be detected, that is, the amplitude and phase.

[0062] Moreover, the electromagnetic wave measuring device 201 is configured to attenuate the laser light R1 with a changeable frequency f1 and extract the laser light R2 with a fixed frequency f2 and the sideband light R1s using the optical filter 111. Therefore, even if the frequency f1 of the laser light R1 outputted by the light emitting element 1a is changed within the frequency range Rf1, the same optical filter 111 can be used to extract the laser light R2 with the frequency f2 and the sideband light R1s with the frequency f1s without changing the optical filter 111, and the beat signal Bs in the IF band with the frequency fs can be obtained using the light receiving element 14. Therefore, the electric field of the electromagnetic wave 36 to be detected can be easily measured while changing the setting of the frequency difference between the laser lights R1 and R2.

[0063] Furthermore, the electromagnetic wave measuring device 201 is configured to extract the laser light R2 and sideband light R1s with a fixed frequency f2 using the optical filter 111, so that the passband F1 of the optical filter 111 can be narrowed and the frequency f1 of the laser light R1 can be set in a wider frequency range Rf1. Therefore, it is possible to satisfactorily measure electromagnetic waves using the laser light R1 set to a suitable frequency f1 while suppressing a decrease in the SNR of the beat signal Bs caused by setting the passband F1 of the optical filter 111 to a wide range.

[0064] The light source unit 101 may be configured to output a laser light R2 whose frequency can be set. That is, the light emitting element 2a may be a wavelength-variable laser, and the frequency f2 of the laser light R2 may be set within a predetermined frequency range Rf2s. In this case, the control unit 31 receives a setting of the frequency f2 from the user of the electromagnetic wave measuring device 201, and controls the frequency f2 of the laser light R2 output by the light emitting element 2a according to the received setting.

[0065] 3, the frequency range Rf2s in which the frequency f2 of the laser light R2 can be set is a range within the passband F1 of the optical filter 111. For example, the frequency range Rf2s is a range in which the frequency f2 of the laser light R2 and the frequency f1s of the sideband light R1s fall within the passband F1 of the optical filter 111.

[0066] (Variation 1) Fig. 4 is a diagram showing a configuration of an electromagnetic wave measuring device according to a first modification of the first embodiment of the present invention. With reference to Fig. 4, compared to the electromagnetic wave measuring device 201, the electromagnetic wave measuring device 202 includes a light source unit 102 instead of the light source unit 101, and an optical filter 112 instead of the optical filter 111. Compared to the light source unit 101, the light source unit 102 includes light emitting elements 1b and 2b instead of the light emitting elements 1a and 2a.

[0067] The light source unit 102 outputs a laser light R1 and a laser light R2 whose frequency can be set. The laser light R1 outputted by the light source unit 102 is an example of a second laser light. The laser light R2 outputted by the light source unit 102 is an example of a first laser light.

[0068] More specifically, the light-emitting element 1b outputs a laser light R1 having a frequency f1. Moreover, the light-emitting element 2b outputs a laser light R2 having a frequency f2. The light-emitting element 1b is, for example, a fixed-wavelength laser, and the frequency f1 of the laser light R1 is set to a predetermined value. The light-emitting element 2b is, for example, a variable-wavelength laser, and the frequency f2 of the laser light R2 can be set within a predetermined frequency range Rf2. More specifically, the control unit 31 receives a setting of the frequency f2 from a user of the electromagnetic wave measuring device 202, and controls the frequency f2 of the laser light R2 output by the light-emitting element 2b according to the received setting.

[0069] The optical shifter 9 shifts the frequency of the laser light R1. More specifically, the optical shifter 9 is provided on an optical transmission path between the light-emitting element 1b and the optical-electromagnetic wave conversion unit 20, and shifts the frequency of the received laser light R1 and outputs it. More specifically, the optical shifter 9 shifts the frequency of the laser light R1 received from the optical brancher 5 by the frequency fs of the oscillation signal received from the oscillator 11, and outputs the shifted laser light R1 to the optical multiplexer 7.

[0070] The optical / electromagnetic wave conversion unit 20 irradiates the electro-optical probe 51 with an electromagnetic wave having a frequency that is the difference between the frequency of the laser light R1, the frequency of which has been shifted by the optical shifter 9, and the frequency of the laser light R2. That is, the optical / electromagnetic wave conversion unit 20 receives the laser lights R1 and R2 from the optical multiplexer 7, generates a detectable electromagnetic wave 36 having a frequency that is the difference between the frequencies of the received laser lights R1 and R2, and irradiates the electro-optical probe 51 with this.

[0071] The optical filter 112 receives the light output from the electro-optic probe 51 and attenuates frequency components outside a predetermined pass band F2. More specifically, the optical filter 112 attenuates components outside the pass band F2 among the frequency components of the light received from the circulator 12. For example, the optical filter 112 is a band pass filter.

[0072] Fig. 5 is a diagram showing the measurement principle of the electromagnetic wave measurement device according to the first modification of the first embodiment of the present invention. With reference to Figs. 4 and 5, in the electromagnetic wave measurement device 202, compared to the electromagnetic wave measurement device 201, the optical filter 112 attenuates the frequency components of the laser light R2 and the sideband light R1s as frequency components outside the passband F2. Specifically, the optical filter 112 attenuates frequency components other than the frequency components of the laser light R1 and the sideband light R2s as frequency components outside the passband F2. That is, the laser light R1 with frequency f1 and the sideband light R2s with frequency f2s are extracted in the optical filter 112 (phase P15).

[0073] Fig. 6 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to the first modification of the first embodiment of the present invention. In Fig. 6, the horizontal axis is optical frequency [Hz]. Referring to Fig. 6, the optical filter 112 passes the laser light R1 of frequency f1 and the sideband light R2s of frequency f2s without attenuation, while attenuating the laser light R2 of frequency f2, the sideband light R1s of frequency f1s, the sideband light R1sd of frequency f1sd, and the sideband light R2sd of frequency f2sd. For example, the passband F2 of the optical filter 112 does not overlap with the frequency range Rf2 in which the frequency f2 of the laser light R2 can be set.

[0074] The optical filter 112 only needs to attenuate at least one of the laser light R2 with frequency f2 and the sideband light R1s with frequency f1s. As an example, the optical filter 112 may pass the sideband light R1s with frequency f1s without attenuating it, or may pass the sideband light R1sd with frequency f1sd without attenuating it. Even in this case, the beat signal Bs can be obtained in the light receiving element 14.

[0075] The electromagnetic wave measuring device 202 is configured to attenuate the laser light R2 with a changeable frequency f2 and extract the laser light R1 with a fixed frequency f1 and the sideband light R2s using the optical filter 112. Therefore, even if the frequency f2 of the laser light R2 outputted by the light-emitting element 2b is changed within the frequency range Rf2, the same optical filter 112 can be used to extract the laser light R1 with the frequency f1 and the sideband light R2s with the frequency f2s without changing the optical filter 112, and the beat signal Bs in the IF band with the frequency fs can be obtained using the light-receiving element 14. Therefore, the electric field of the electromagnetic wave 36 to be detected can be easily measured while changing the setting of the frequency difference between the laser lights R1 and R2.

[0076] Furthermore, the electromagnetic wave measuring device 202 is configured to extract the laser light R1 and sideband light R2s with a fixed frequency f1 using the optical filter 112, so that the passband F2 of the optical filter 112 can be narrowed and the frequency f2 of the laser light R2 can be set in a wider frequency range Rf2. Therefore, it is possible to satisfactorily measure electromagnetic waves using the laser light R2 set to a suitable frequency f2 while suppressing a decrease in the SNR of the beat signal Bs caused by setting the passband F2 of the optical filter 112 to a wide range.

[0077] (Variation 2) Fig. 7 is a diagram showing a configuration of an electromagnetic wave measuring device according to Modification 2 of the first embodiment of the present invention. With reference to Fig. 7, compared to electromagnetic wave measuring device 201, electromagnetic wave measuring device 203 includes optical filter 113 instead of optical filter 111.

[0078] The optical filter 113 receives the light output from the electro-optic probe 51 and attenuates frequency components outside a predetermined pass band F3. More specifically, the optical filter 113 attenuates components outside the pass band F3 among the frequency components of the light received from the circulator 12. For example, the optical filter 113 is a band elimination filter.

[0079] Fig. 8 is a diagram showing the measurement principle of an electromagnetic wave measurement device according to Modification 2 of the first embodiment of the present invention. With reference to Fig. 7 and Fig. 8, in electromagnetic wave measurement device 203, compared to electromagnetic wave measurement device 201, optical filter 113 attenuates the frequency components of laser light R2 and sideband light R1s as frequency components outside passband F3. That is, in optical filter 113, laser light R1 with frequency f1 and sideband light R2s with frequency f2s are extracted (phase P15).

[0080] 9 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to the second modification of the first embodiment of the present invention. In FIG. 9, the horizontal axis is optical frequency [Hz]. Referring to FIG. 9, the optical filter 113 passes the laser light R1 of frequency f1, the sideband light R2s of frequency f2s, the sideband light R1sd of frequency f1sd, and the sideband light R2sd of frequency f2sd without attenuation, while attenuating the laser light R2 of frequency f2 and the sideband light R1s of frequency f1s. For example, the passband F3 of the optical filter 113 does not overlap with the frequency range Rf1 in which the frequency f1 of the laser light R1 can be set.

[0081] The optical filter 113 only needs to attenuate at least one of the laser light R2 with frequency f2 and the sideband light R1s with frequency f1s. That is, the optical filter 113 may pass either the sideband light R1s with frequency f1s or the laser light R2 with frequency f2 without attenuating it. Even in this case, the beat signal Bs can be obtained in the light receiving element 14.

[0082] The electromagnetic wave measuring device 203 is configured to attenuate the laser light R2 with a fixed frequency f2 and extract the laser light R1 with a variable frequency f1 and the sideband light R2s using the optical filter 113. Therefore, even if the frequency f1 of the laser light R1 outputted by the light emitting element 1a is changed within the frequency range Rf1, the same optical filter 113 can be used to extract the laser light R1 with the frequency f1 and the sideband light R2s with the frequency f2s without changing the optical filter 113, and the beat signal Bs in the IF band with the frequency fs can be obtained using the light receiving element 14. Therefore, the electric field of the electromagnetic wave 36 to be detected can be easily measured while changing the setting of the frequency difference between the laser lights R1 and R2.

[0083] (Variation 3) Fig. 10 is a diagram showing a configuration of an electromagnetic wave measuring device according to a third modification of the first embodiment of the present invention. With reference to Fig. 10, compared to the electromagnetic wave measuring device 202, the electromagnetic wave measuring device 204 includes an optical filter 114 instead of the optical filter 112.

[0084] The optical filter 114 receives the light output from the electro-optic probe 51 and attenuates frequency components outside a predetermined pass band F4. More specifically, the optical filter 114 attenuates components outside the pass band F4 among the frequency components of the light received from the circulator 12. For example, the optical filter 114 is a band elimination filter.

[0085] Fig. 11 is a diagram showing the measurement principle of an electromagnetic wave measurement device according to Modification 3 of the first embodiment of the present invention. With reference to Fig. 10 and Fig. 11, in the electromagnetic wave measurement device 204, compared to the electromagnetic wave measurement device 202, the optical filter 114 attenuates the frequency components of the laser light R1 and the sideband light R2s as frequency components outside the passband F4. That is, in the optical filter 114, the laser light R2 with frequency f2 and the sideband light R2s with frequency f1s are extracted (phase P15).

[0086] Fig. 12 is a diagram showing an example of a passband of an optical filter in an electromagnetic wave measuring device according to the third modification of the first embodiment of the present invention. In Fig. 12, the horizontal axis is optical frequency [Hz]. Referring to Fig. 12, the optical filter 114 passes the laser light R2 of frequency f2, the sideband light R1s of frequency f1s, the sideband light R1sd of frequency f1sd, and the sideband light R2sd of frequency f2sd without attenuation, while attenuating the laser light R1 of frequency f1 and the sideband light R2s of frequency f2s. For example, the passband F4 of the optical filter 114 does not overlap with the frequency range Rf2 in which the frequency f2 of the laser light R2 can be set.

[0087] The optical filter 114 only needs to attenuate at least one of the laser light R1 with frequency f1 and the sideband light R2s with frequency f2s. In other words, the optical filter 114 may pass either the sideband light R2s with frequency f2s or the laser light R1 with frequency f1 without attenuating it. Even in this case, the beat signal Bs can be obtained in the light receiving element 14.

[0088] The electromagnetic wave measuring device 204 is configured to attenuate the laser light R1 with a fixed frequency f1 and extract the laser light R2 with a variable frequency f2 and the sideband light R1s using the optical filter 114. Therefore, even if the frequency f2 of the laser light R2 outputted by the light emitting element 2b is changed within the frequency range Rf2, the same optical filter 114 can be used to extract the laser light R1 with the frequency f1 and the sideband light R2s with the frequency f2s without changing the optical filter 114, and the beat signal Bs in the IF band with the frequency fs can be obtained using the light receiving element 14. Therefore, the electric field of the detected electromagnetic wave 36 can be easily measured while changing the setting of the frequency difference between the laser lights R1 and R2.

[0089] [Operation flow] The electromagnetic wave measuring device according to the embodiment of the present invention includes a computer including a memory, and a processor such as a CPU in the computer reads out a program including some or all of the steps of the following flowcharts from the memory and executes it. The program of this device can be installed from the outside. The program of this device is distributed in a state stored in a recording medium or via a communication line.

[0090] 13 is a diagram showing the procedure of an electromagnetic wave measuring method using the electromagnetic wave measuring device according to the first embodiment of the present invention. 13 shows the procedure of an electromagnetic wave measuring method using the electromagnetic wave measuring device 201.

[0091] Referring to FIG. 13, first, the frequency f1 of the laser light R1 is set in the frequency range Rf1 (step S11).

[0092] Next, laser light R1 and laser light R2 having the set frequency f1 are generated (step S12).

[0093] Next, the generated laser beams R1, R2 and the electromagnetic wave to be detected 36 are applied to the electro-optical probe 51 (step S13).

[0094] Next, the optical filter 111 is used to attenuate frequency components outside the passband F1 of the light output from the electro-optical probe 51. More specifically, the electro-optical probe 51 outputs the laser lights R1 and R2 and the sideband lights R1s and R2s to the optical filter 111. The optical filter 111 is used to attenuate frequency components outside the passband F1, excluding the frequency components of the laser light R2 and the sideband light R1s (step S14).

[0095] Next, the light that has passed through the optical filter 111 is converted into a beat signal Bs by using the light receiving element 14 (step S15).

[0096] Next, the amplitude and phase of the converted beat signal Bs are detected using the amplitude / phase detector 15 (step S16).

[0097] In the electromagnetic wave measuring method using the electromagnetic wave measuring device 202 of the first modified example, in step S11, the frequency f2 of the laser light R2 is set in the frequency range Rf2, and in step S14, the optical filter 112 is used to attenuate frequency components outside the pass band F2 of the light output from the electro-optical probe 51.

[0098] In addition, in the electromagnetic wave measuring method using the electromagnetic wave measuring device 203 of the second modification, in step S14, the optical filter 113 is used to attenuate frequency components outside the passband F3 of the light output from the electro-optical probe 51.

[0099] Moreover, in the electromagnetic wave measuring method using the electromagnetic wave measuring device 203 according to the third modification, in the above step S11, the frequency f2 of the laser light R2 is set in the frequency range Rf2, and in the above step S14, the optical filter 114 is used to attenuate frequency components outside the pass band F4 of the light output from the electro-optical probe 51.

[0100] Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0101] <Second embodiment> [Configuration and basic operation] This embodiment relates to an electromagnetic wave measuring device 205 that performs asynchronous measurement, as compared with the electromagnetic wave measuring devices 201, 202, 203, and 204 according to the first embodiment. Contents other than those described below are the same as those of the electromagnetic wave measuring device 201 according to the first embodiment.

[0102] Fig. 14 is a diagram showing a configuration of an electromagnetic wave measuring device according to a second embodiment of the present invention. Referring to Fig. 14, compared to the electromagnetic wave measuring device 201, the electromagnetic wave measuring device 205 does not include the optical splitters 5 and 6, the optical multiplexer 7, the optical shifter 9, the oscillator 11, and the optical-electromagnetic wave converting unit 20. The electromagnetic wave measuring device 205 measures the electromagnetic wave 37 to be detected. The electromagnetic wave 37 to be detected is, for example, an electromagnetic wave in the RF band. The electromagnetic wave measuring device 205 performs asynchronous measurement in which the electromagnetic wave 37 to be detected and the probe light are not synchronized. Here, if the frequency of the electromagnetic wave 37 to be detected is fEM, then the relationship fEM ≠ f2-f1 is satisfied.

[0103] The optical amplifiers 3 and 4 amplify the laser beams R 1 and R 2 outputted from the light source unit 101 and output them to the optical multiplexer 8 .

[0104] The optical multiplexer 8 multiplexes the laser beams R 1 and R 2 received from the optical amplifiers 3 and 4 , and outputs the multiplexed laser beams to the electro-optic probe 51 via the circulator 12 .

[0105] The electro-optical probe 51 receives the laser beams R1 and R2 outputted by the light source unit 101 and the detectable electromagnetic wave 37. The electro-optical probe 51 detects the detectable electromagnetic wave 37. More specifically, the light transmitted from the circulator 12 to the electro-optical probe 51 interacts with the detectable electromagnetic wave 37 in the electro-optical probe 51, is reflected and outputted to the circulator 12, and is outputted from the circulator 12 to the optical filter 111.

[0106] The optical filter 111 receives the light output from the electro-optic probe 51 and attenuates frequency components outside a predetermined pass band F1. More specifically, the optical filter 111 attenuates components outside the pass band F1 among the frequency components of the light received from the circulator 12. For example, the optical filter 111 is a band pass filter.

[0107] Fig. 15 is a diagram showing the measurement principle of the electromagnetic wave measuring device according to the second embodiment of the present invention. For ease of understanding, a case in which the detected electromagnetic wave 37 is a CW will be described with reference to Figs. 14 and 15.

[0108] The detected electromagnetic wave 37 having a frequency of fEM is irradiated in the direction of the electro-optic crystal in the electro-optic probe 51 (phase P1). In addition, the laser light R1 with frequency f1 and the laser light R2 with frequency f2 combined in the optical combiner 8 (phase P11) are transmitted as probe light to the electro-optic crystal in the electro-optic probe 51 (phase P12).

[0109] The electro-optical probe 51 outputs to the optical filter 111 the laser beams R1 and R2, the sideband beams R1s and R1sd generated by modulating the laser beam R1, and the sideband beams R2s and R2sd generated by modulating the laser beam R2.

[0110] More specifically, the frequency f1 component of the probe light is modulated in the electro-optic crystal irradiated with the electromagnetic wave 37 to generate sideband light R1s with a frequency component of f1s (=f1+fEM) and sideband light R1sd with a frequency component of f1sd (=f1-fEM). The frequency f2 component of the probe light is modulated in the electro-optic crystal irradiated with the electromagnetic wave 37 to generate sideband light R2s with a frequency component of f2s (=f2-fEM) and sideband light R2sd with a frequency component of f2sd (=f2+fEM) (phase P13). These generated lights are transmitted to the optical filter 111 together with the probe lights with frequencies f1 and f2 (phase P14).

[0111] The optical filter 111 attenuates the frequency components of the laser light R1 and the sideband light R2s as frequency components outside the passband F1. Specifically, the optical filter 111 attenuates frequency components other than the frequency components of the laser light R2 and the sideband light R1s as frequency components outside the passband F1. That is, the optical filter 111 extracts the laser light R2 with frequency f2 and the sideband light R1s with frequency f1s (phase P15).

[0112] The light extracted by the optical filter 111 is transmitted to the light receiving element 14 and photoelectrically converted, thereby obtaining a beat signal Bs in the IF band of f2-f1s=fIF (phase P21).

[0113] Note that the electromagnetic wave measuring device 205 may be configured to include a light source unit 102 instead of the light source unit 101 and an optical filter 112 instead of the optical filter 111, similar to the first modification described above.

[0114] Furthermore, the electromagnetic wave measuring device 205 may be configured to include an optical filter 113 instead of the optical filter 111, as in the second modification example described above.

[0115] Furthermore, the electromagnetic wave measuring device 205 may be configured to include a light source unit 102 instead of the light source unit 101 and an optical filter 114 instead of the optical filter 111, as in the third modification example described above.

[0116] The above-described embodiments should be considered as illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0117] 1a, 2a, 1b, 2b Light emitting element 3,4 Optical amplifier 5,6 Optical splitter 7,8 Optical multiplexer 9 Optical Shifter 11 Oscillators 12 Circulator 14 Photodetector 15 Amplitude / Phase Detector 16 Optical Fiber 20 Optical electromagnetic wave conversion section 21 Photoelectric converter 22 Antenna 31 Control Unit 36,37 Detected electromagnetic waves 51 Electro-Optical Probe 101,102 Light source section 111,112,113,114 Optical filters 201,202,203,204,205 Electromagnetic wave measuring device F1, F2, F3, F4 passband Rf1, Rf2, Rf3, Rf4 frequency range

Claims

1. a light source unit that outputs a first laser light and a second laser light, the frequencies of which can be set within a predetermined frequency range; an electro-optical probe for receiving the first laser light, the second laser light, and a detected electromagnetic wave, each having a frequency set within the frequency range; an optical filter that receives the light output from the electro-optic probe and attenuates frequency components outside a predetermined passband; a light receiving element that converts light that has passed through the optical filter into an electrical signal; the electro-optical probe outputs the first laser light, the second laser light, a first sideband light generated by modulating the first laser light, and a second sideband light generated by modulating the second laser light to the optical filter; an optical filter that attenuates at least one of the frequency components of the first laser light and the second sideband light as frequency components outside the passband, or attenuates at least one of the frequency components of the second laser light and the first sideband light as frequency components outside the passband, the electromagnetic wave measuring device;

2. the optical filter is a bandpass filter, 2. The electromagnetic wave measuring device according to claim 1, wherein the optical filter attenuates at least one of a frequency component of the first laser light and a frequency component of the second sideband light as a frequency component outside the passband.

3. the optical filter is a band elimination filter, 2. The electromagnetic wave measuring device according to claim 1, wherein the optical filter attenuates at least one of a frequency component of the second laser light and a frequency component of the first sideband light as a frequency component outside the passband.

4. 4. The electromagnetic wave measuring device according to claim 1, wherein a pass band of the optical filter does not overlap with the frequency range.

5. The electromagnetic wave measuring device further comprises: an optical shifter that shifts the frequency of the first laser light; 4. The electromagnetic wave measuring device according to claim 1, further comprising an optical-electromagnetic wave conversion unit that irradiates the electro-optical probe with an electromagnetic wave having a frequency that is a difference between the frequency of the first laser light whose frequency has been shifted by the optical shifter and the frequency of the second laser light.

6. The electromagnetic wave measuring device further comprises: an optical shifter that shifts the frequency of the second laser light; 4. The electromagnetic wave measuring device according to claim 1, further comprising an optical-electromagnetic wave conversion unit that irradiates the electro-optical probe with an electromagnetic wave having a frequency that is a difference between the frequency of the first laser light and the frequency of the second laser light whose frequency has been shifted by the optical shifter.

7. The electromagnetic wave measuring device according to claim 1 , wherein the light source unit outputs the second laser light whose frequency can be set.

8. An electromagnetic wave measuring method in an electromagnetic wave measuring device, comprising: setting a frequency in a predetermined frequency range; generating a first laser beam and a second laser beam having a frequency set within the frequency range; providing the generated first laser light, the second laser light, and the detected electromagnetic wave to an electro-optical probe; using an optical filter to attenuate frequency components of the light output from the electro-optic probe that are outside a predetermined passband; and converting the light passing through the optical filter into an electrical signal using a light receiving element. the electro-optical probe outputs the first laser light, the second laser light, a first sideband light generated by modulating the first laser light, and a second sideband light generated by modulating the second laser light to the optical filter; In the step of attenuating frequency components outside the passband, at least one of the frequency components of the first laser light and the frequency components of the second sideband light is attenuated as the frequency components outside the passband, or at least one of the frequency components of the second laser light and the frequency components of the first sideband light is attenuated.

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